This is a class of [[Projections|projections]] for mapping a portion of the surface of a sphere to a flat image, typically a camera's film or detector plane. In a fisheye projection the distance from the centre of the image to a point is close to proportional to the true angle of separation.

This is a class of [[Projections|projections]] for mapping a portion of the surface of a sphere to a flat image, typically a camera's film or detector plane. In a fisheye projection the distance from the centre of the image to a point is close to proportional to the true angle of separation.

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Commonly there are two types of fisheye distinguished: circular [[fisheyes]] and fullframe [[fisheyes]]. However, both follow the same projection geometrics. The only difference is one of [[field of view]]: for a circular fisheye the circular image fits (more or less) completely in the frame, leaving blank areas in the corner. For the full frame variety, the image is over-filled by the circular fisheye image, leaving no blank space on the film or detector. A circular fisheye can be made full frame if you use it with a smaller sensor/film size (and vice versa), or by zooming a fisheye adaptor on a zoom lens.

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Commonly there are two types of fisheye distinguished: circular [[fisheyes]] and fullframe [[fisheyes]]. However, both follow the same projection geometrics. The only difference is one of [[Field of View]]: for a circular fisheye the circular image fits (more or less) completely in the frame, leaving blank areas in the corner. For the full frame variety, the image is over-filled by the circular fisheye image, leaving no blank space on the film or detector. A circular fisheye can be made full frame if you use it with a smaller sensor/film size (and vice versa), or by zooming a fisheye adaptor on a zoom lens.

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There is no single fisheye projection, but instead there are a class of projection transformation all referred to as ''fisheye'' by various lens manufacturers, with names like ''equisolid angle projection'', or ''equidistance fisheye''. Less common are traditional spherical projections which map to circular images, such as the [http://mathworld.wolfram.com/OrthographicProjection.html orthographic] (lenses commonly designated ''OP'') or [http://mathworld.wolfram.com/StereographicProjection.html stereographic] projections. Luckily, most of these related projections can be dealt with in a simple way. The following explanation is taken from a posting by [[Helmut Dersch]] (link to original see below):

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There is no single fisheye projection, but instead there are a class of projection transformation all referred to as ''fisheye'' by various lens manufacturers, with names like ''equisolid angle projection'', or ''equidistance fisheye''. Less common are traditional spherical projections which map to circular images, such as the [http://mathworld.wolfram.com/OrthographicProjection.html orthographic] (lenses commonly designated ''OP'') or [[Stereographic Projection|stereographic]] projections. Luckily, [[Panorama tools]] and [[Hugin]] can deal with most of these mentioned projections.

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'''theta''' is the angle between a point in the real world and the optical axis, which goes from the center of the image through the center of the lens.

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'''<math>\theta\,</math>''' is the angle in rad between a point in the real world and the optical axis, which goes from the center of the image through the center of the lens, <math>f</math> is the focal length of the lens and <math>R</math> is radial position of a point on the image on the film or sensor.

More information on [[fisheyes]] and their distortions in this [http://www.coastalopt.com/pdfs/FisheyeComparison_SPIE.pdf PDF from coastal optics]

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(Content partly based on a mail by Helmut Dersch which can be found at W.J. Markerink's <strike>[http://www.a1.nl/phomepag/markerink/fishyfaq.htm page about fisheye analysis]</strike> Link not valid anymore)

[[Category:Glossary]]

[[Category:Glossary]]

Latest revision as of 19:46, 7 May 2013

Circular Fisheye projection, with permission from Ben Kreunen

Fullframe Fisheye projection, with permission from Ben Kreunen

This is a class of projections for mapping a portion of the surface of a sphere to a flat image, typically a camera's film or detector plane. In a fisheye projection the distance from the centre of the image to a point is close to proportional to the true angle of separation.

Commonly there are two types of fisheye distinguished: circular fisheyes and fullframe fisheyes. However, both follow the same projection geometrics. The only difference is one of Field of View: for a circular fisheye the circular image fits (more or less) completely in the frame, leaving blank areas in the corner. For the full frame variety, the image is over-filled by the circular fisheye image, leaving no blank space on the film or detector. A circular fisheye can be made full frame if you use it with a smaller sensor/film size (and vice versa), or by zooming a fisheye adaptor on a zoom lens.

There is no single fisheye projection, but instead there are a class of projection transformation all referred to as fisheye by various lens manufacturers, with names like equisolid angle projection, or equidistance fisheye. Less common are traditional spherical projections which map to circular images, such as the orthographic (lenses commonly designated OP) or stereographic projections. Luckily, Panorama tools and Hugin can deal with most of these mentioned projections.

is the angle in rad between a point in the real world and the optical axis, which goes from the center of the image through the center of the lens, is the focal length of the lens and is radial position of a point on the image on the film or sensor.